The invention relates to an imaging system for an object hidden inside a high-diffraction medium and an imaging method thereof, and belongs to the fields of diffraction imaging and digital holography. A charge coupled device (CCD) camera is arranged above the system, and a diffraction medium, a sample and a linear translation platform are arranged below the system; ground glass is connected on the linear translation platform; a plane mirror, a pinhole, a microobjective and a plane mirror set are arranged on one side of the diffraction medium sequentially; a beam splitting crystal and the linear translation platform are arranged below the ground glass sequentially; the plane mirror set is connected on the linear translation platform; and a convex lens and a laser diode are arranged on one side, which is away from the microobjective, of the beam splitting crystal sequentially. The imaging method comprises the following steps of: 1, moving the linear translation platform, so that the optical distance of object light is equal to that of reference light; 2, recording a hologram once in a computer every time the linear translation platform moves in a light path, and recording N holograms, wherein the optimum value of N is 60; and 3, representing the N holograms respectively by using a Fresnel diffraction integral formula, and overlapping the N holograms finally. By the imaging system and the imaging method, the problem of the direct imaging of the object inside the high-diffraction medium is solved.